Ergonomics is one of those "squishy" subjects that a lot of people claim expertise about. In our role as furniture specifiers, we are often asked for our input on whether a certain chair is "ergonomic". To help us objectively determine ergonomic properties, my staff relies on the Business and Institutional Furniture Manufacturer's Association (BIFMA), Ultimate Test for Fit.
The UTFF is outlined below:
(7.1) SEAT HEIGHT
Users should be able to sit with their feet comfortably on the floor or footrest without undue pressure on the underside of the thighs. The thigh-to-torso angle should not be less than 90°.
(7.2) SEAT DEPTH
Users should be able to sit in the chair without undue pressure against the back of the knees, their back properly supported by the backrest and with adequate buttock and thigh support.
(7.3) SEAT WIDTH
The seat should be wider than the hip breadth of the user with allowance for movement and clothing. The seat width should not limit the ability to use the armrests comfortably.
(7.4) SEAT PAN ANGLE
This should allow users to support their feet on the floor or footrest. They should not cause the user’s torso-to-thigh angle to be less than 90°. Forward seat pan angles should not cause users to shift excessive weight to their feet or experience the sensation of sliding out of the chair.
(7.5) BACK SUPPORT
(7.5.1) SEAT BACKREST HEIGHT
All backrests should provide adequate lumbar support and buttocks clearance. For tasks requiring upper body mobility, the backrest should not interfere with the user’s movement. For users who prefer reclining postures or greater upper back support, the back height should provide support for the shoulder blades.
(7.5.2) BACKREST WIDTH
The width of the backrest should provide adequate support for the curvature of the user’s back without causing localized pressure points.
(7.5.3) LUMBAR SUPPORT
The height and shape of the lumbar support should coincide with the lumbar curve (“the small”) of the user’s back. The support should be firm, but not cause localized pressure points.
(7.6) MOVEMENTS OF THE SEAT PAN AND BACK SUPPORT
The user should be able to sit in a position where the torso-to-thigh angle is equal to or greater than 90°. The seat and backrest angles should accommodate the varying postures assumed by the user throughout the day.
(7.7) ARM SUPPORT
(7.7.1) ARMREST HEIGHT
This should allow users to sit in a variety of postures while supporting their forearms and/or elbows in a manner that avoids lifting the shoulders (armrests too high) or leaning to the side to reach the armrest (armrests too low). The armrest height should allow accessibility to, and performance of, tasks.
(7.7.2) ARMREST LENGTH
The length of the armrest should allow users to sit close enough to the work surface to perform their tasks while maintaining contact with the backrest.
(7.7.3) INSIDE DISTANCE BETWEEN ARMRESTS
Armrests should allow users to sit in a variety of postures while supporting their forearms in a manner that avoids lifting the shoulders and/or excessive outward positioning of the elbows. Armrests should allow accessibility to, and performance of, tasks. The inside distance between the armrests should allow the user to enter and exit the chair easily. The hips should comfortably fit between the armrests or supports.
For more information on seating ergonomics, visit Office Master's Ergonomic University.
The UTFF is outlined below:
(7.1) SEAT HEIGHT
Users should be able to sit with their feet comfortably on the floor or footrest without undue pressure on the underside of the thighs. The thigh-to-torso angle should not be less than 90°.
(7.2) SEAT DEPTH
Users should be able to sit in the chair without undue pressure against the back of the knees, their back properly supported by the backrest and with adequate buttock and thigh support.
(7.3) SEAT WIDTH
The seat should be wider than the hip breadth of the user with allowance for movement and clothing. The seat width should not limit the ability to use the armrests comfortably.
(7.4) SEAT PAN ANGLE
This should allow users to support their feet on the floor or footrest. They should not cause the user’s torso-to-thigh angle to be less than 90°. Forward seat pan angles should not cause users to shift excessive weight to their feet or experience the sensation of sliding out of the chair.
(7.5) BACK SUPPORT
(7.5.1) SEAT BACKREST HEIGHT
All backrests should provide adequate lumbar support and buttocks clearance. For tasks requiring upper body mobility, the backrest should not interfere with the user’s movement. For users who prefer reclining postures or greater upper back support, the back height should provide support for the shoulder blades.
(7.5.2) BACKREST WIDTH
The width of the backrest should provide adequate support for the curvature of the user’s back without causing localized pressure points.
(7.5.3) LUMBAR SUPPORT
The height and shape of the lumbar support should coincide with the lumbar curve (“the small”) of the user’s back. The support should be firm, but not cause localized pressure points.
(7.6) MOVEMENTS OF THE SEAT PAN AND BACK SUPPORT
The user should be able to sit in a position where the torso-to-thigh angle is equal to or greater than 90°. The seat and backrest angles should accommodate the varying postures assumed by the user throughout the day.
(7.7) ARM SUPPORT
(7.7.1) ARMREST HEIGHT
This should allow users to sit in a variety of postures while supporting their forearms and/or elbows in a manner that avoids lifting the shoulders (armrests too high) or leaning to the side to reach the armrest (armrests too low). The armrest height should allow accessibility to, and performance of, tasks.
(7.7.2) ARMREST LENGTH
The length of the armrest should allow users to sit close enough to the work surface to perform their tasks while maintaining contact with the backrest.
(7.7.3) INSIDE DISTANCE BETWEEN ARMRESTS
Armrests should allow users to sit in a variety of postures while supporting their forearms in a manner that avoids lifting the shoulders and/or excessive outward positioning of the elbows. Armrests should allow accessibility to, and performance of, tasks. The inside distance between the armrests should allow the user to enter and exit the chair easily. The hips should comfortably fit between the armrests or supports.
For more information on seating ergonomics, visit Office Master's Ergonomic University.
